Hi.I am making a line follower robot using qtr-8rc sensor array and arduino uno. While calibrating the sensors using QTRRCExample, I found that I got desirable result while testing the array with a black line on white surface. But when it comes to white line on a black surface,I’m not getting the desired position value.

Did you set the whiteLine argument to 1 for the readLine function in the main loop of the QTRRCExample code? It might be helpful for you to read this post that explains the purpose of the whiteLine argument in the readLine method of the QTRSensor library. For more details about that method and its parameters, see its function definition in QTRSensors.cpp.